Ulrich Horbach

Real-time rendering of dynamic scenes using wave field synthesis

Wave field synthesis (WFS) methods, combined with the MPEG-4 multimedia standard, allow us to capture, transmit and reproduce time-varying acoustic scenes, such as theatre events with moving actors in a concert hall, in a perceptually realistic way for groups of listeners in a defined listening area. In this paper, we present related techniques that have been developed within the European project Carrouso.

Process and device for mixing sound signals

The present invention is directed to a process and device for mixing a plurality of sound signals. The process includes separating each sound signal and selectively delaying each separated sound signal. The process also includes selectively weighting each separated and selectively delayed sound signal and adding corresponding ones of the selectively weighted signals to an intermediary signal. The process also includes separating and filtering each intermediary signal, and adding the intermediary signals to form an output signal. The device for mixing sound signals of a plurality of input channels into a plurality of output channels includes each input channel having a plurality of partial channels, a decoder providing the plurality of outputs, and a plurality of intermediary channels coupled to the plurality of partial channels and to the decoder.

Binaural room scanning—A new tool for acoustic and psychoacoustic research

A new technology called ‘‘ binaural room scanning’’ (BRS) is introduced, allowing real‐time virtual loudspeaker reproduction in any virtual room. It is based on a special convolution algorithm for auralization and on the involvement of spontaneous head movements by means of a head‐tracking system. A complete set of relevant dummy head HRTFs is measured for each loudspeaker and the resulting response in the original room. The data are stored and used for convolution. Thus the BRS system does not apply room synthesis methods (e.g., ray‐tracing), but, in contrast, enables accurate virtual binaural listening in a real (cloned) loudspeaker reproduction room. Since natural head movements are realizable in the simulated sound field, it offers new possibilities in the application of listening tests, not only in the area of room acoustics and loudspeaker reproduction, but also for psychoacoustic research. Examples will be reported.

Perceptual encoding of acoustic environments

Wave field synthesis (WFS) methods, combined with the MPEG-4 standard, allow capturing, transmitting, and reproducing time-varying acoustic scenes. The MPEG-4 standard allows transmission of a set of recorded audio signals together with a parametric description of the acoustic environment. To allow for moving sources in a given environment a parametric perceptual model of the acoustic environment is presented. The acoustic environment is then recreated at the listeners end in the decoder depending on the exact loudspeaker setup and the position of the virtual sources in the reproduction area. A perceptual encoding mechanism for acoustic environments is introduced that allows a perceptually realistic experience for a group of listeners in a defined listening area. We present techniques that have been partly developed within the European project Carrouso and by Pellegrini (see Ph. D. Thesis, Ruhr-University Bochum, Germany, 2000).